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1.
《African Journal of Marine Science》2013,35(3):291-304
Studies to understand local-scale patterns in the recruitment of juvenile coral-reef fishes within the western Indian Ocean (WIO) region are few, yet such knowledge is important in fisheries management. Underwater visual census surveys were conducted at five shallow fringing-lagoon reef sites along the Kenyan coast, between June 2012 and March 2016, to quantify patterns in the abundance of new recruits and juveniles. Recruitment was observed year-round, with a consistent pronounced seasonal peak in recruit densities and species richness during December to April of each year, which was strongly correlated with high sea temperatures. Annual variations in recruitment were also observed, with a higher recruitment peak in 2013 as compared with in other years. A total of 112 species belonging to 19 families were identified, dominated by species belonging to the Pomacentridae, Labridae and Apogonidae, which altogether represented 91% of the total number of recruits recorded. The species with the largest number of recruits (Chromis viridis, Thalassoma hebraicum and Gomphosus caeruleus) showed evidence of year-round recruitment, although the timing of recruitment peaks was not consistent. Multivariate analysis of the species composition separated mainland from offshore fringing-reef sites, and also revealed strong habitat associations, pointing towards increasing recruit abundance with increasing live hard-coral cover and rugosity. Live hard-coral cover, which constituted an average of 21%, was associated with 63% of the total number of recruits recorded. This study contributes new insight into local-scale patterns of juvenile reef-fish recruitment in Kenya and the WIO region, and demonstrates the important nursery function of shallow fringing-lagoon reefs. 相似文献
2.
The behavior of the coastal system represented by Nyiskii Inlet (lagoon) and Plastun Spit is investigated by modeling morphodynamic processes. The observable advance of Plastun Spit and displacement of the Anuchin Strait are explained by changes in the alongshore sediment flux transporting material to the end of the spit from the south. It is shown that severe storms combined with a surge and tide tend to deepen the lagoon bottom. The model of a tidal inlet system is proposed to describe the evolution of tidal flats under conditions of a relative rise in sea level. It is concluded that the volume of tidal flats can be reduced several times in the next 100 years. This trend should accelerate erosion of the inlet coasts due to decreased dissipation of the energy received from the open sea. 相似文献
3.
《Marine Geology》2004,203(1-2):161-176
The method for the sequential extraction of P proposed by Jensen et al. [Mcglathery, K.J., Marino, R., Howarth, R.W. (1998) Limnol. Oceanogr. 43, 799–810] was used to study the spatial distribution of sedimentary P in superficial sediments of a mesohaline coastal lagoon located in a watershed formed by carboniferous sandstone in the Western Mediterranean (Minorca Island, Spain). Dissolved inorganic phosphate (IP), dissolved organic phosphate (OP), Fe, Ca, Al, and F were analyzed in the extractions to assess adequacy of this method to clay sediments. The elemental composition of the solid phase (Al, Fe, K, Ti, Si, Mg and Ca) was also analyzed to relate concentrations of P pools to the mineral composition. Samples from marine carbonated sediments, rock and some materials of biological origin (tubes of polychaete Ficopomatus enigmaticus, bivalve shell debris) were analyzed for comparative purposes. The sequential procedure allowed to extract almost all sedimentary P from carbonate sediments and biogenic debris, but only 70% of total phosphorus (TP) from clay sediments and rock. Main IP pools in the lagoon were Fe-bound P (16.6% of TP), CaCO3-bound P mainly from Ficopomatus tubes (12.0% of TP), and detrital carbonate fluorapatite (7.8% of TP). The most abundant P pool was refractory P (20.3% of TP), which appeared associated to the (Fe,K)Al-silicate fraction and to humic P. This indicated that clay–humic–organic P complexes were the main P reservoir in the lagoon. Spatial distribution of P pools reflected differential sedimentation of allochthonous materials, authigenic precipitation of Fe-oxides, and Fe-bound P as well as the differential distribution of organisms such as Ficopomatus. 相似文献
4.
《Estuarine, Coastal and Shelf Science》2003,56(3-4):433-445
Grazing of the copepods Acartia clausi and Pseudodiaptomus hessei on natural particles was studied from on board experiments during several 24 h time series performed between 1993 and 1997 in four sites of the Ebrié Lagoon (Côte d'Ivoire). Ingestion rates of both species increased linearly with food concentration until a concentration threshold (5.5×109 μm3 l−1 for A. clausi and 5.2×109 mm3 l−1 for P. hessei) beyond which the relation presented a plateau. Both species poorly selected the peak of available particles (range 3–6 mm equivalent spherical diameter, ESD) but A. clausi seek preferentially smaller particles (6–21 μm ESD) than P. hessei (9–33 μm ESD). When the proportion of the preferred particles in the food offered decreased, A. clausi extended its selectivity towards both smaller and larger particles whereas P. hessei extended its selectivity towards larger particles only. As a consequence of these patterns, the useful particle concentration (UPC) was higher for A. clausi than for P. hessei. In addition, the ratio of the UPC for the two species showed a positive relationship with the ratio of their respective biomass. The significance of these results for the adaptation capacities of the two species and for the ecosystem functioning are discussed. A. clausi which is more suited than P. hessei to exploit smaller particles (3–6 μm) which dominate the seston, has a food competitive advantage. The inadequacy between the seston food-size composition and the selective patterns of the two main zooplankton species of the Ebrié Lagoon explains that they could be food limited despite the high trophic level of the lagoon. It could also partly explain the low transfer efficiency between phytoplankton and zooplankton in this ecosystem. 相似文献
5.
The macroalga Caulerpa prolifera colonized the Mar Menor coastal lagoon after the enlargement of the main inlet in 1972, coexisting now with the previous Cymodocea nodosa meadows. The physiological response and the photoacclimation capacity of both species were studied. For this purpose in vivo chlorophyll a fluorescence, photoprotective mechanisms and oxidative stress were measured in both species in summer 2010 and exposure-recovery experiments were conducted to determine the acclimation capacity of both species. The results suggest that C. prolifera behaves as a shade-adapted species with a low photoprotective capacity, light being one of the main factors governing its distribution in the lagoon. The high photosynthetic capacity and lack of photoinhibition found in C. nodosa suggest that this species is highly photoprotected. It also possesses a high concentration of lutein and a high de-epoxidation degree, related to a much higher NPQmax value. 相似文献